The invention relates to a process for the manufacture of a frozen base composition having a high surface area to volume ratio to facilitate easy mixing with added liquid to make frozen beverages such as milk shakes or smoothies or other frozen ice drinks such as frozen margueritas or daiquiris. In particular, the use of a post-extrusion, secondary freezing step to further cool a frozen aerated ice confection or dessert to a temperature near its glass transition temperature followed by the alteration of the physical dimensions of the further cooled product results in aerated ice confection particles having a substantial increase in the surface area to volume ratio such that they are highly useful for forming such frozen beverages.
Ice particles are needed in order to form frozen ice drinks. Various mechanical means are used to crush ice cubes or blocks to the desired size for use in such products. Alternatively, ice particles can be made by cooling water droplets to low temperatures. The glass transition temperature (Tg) of pure water is −130° C. but the formation of a solution by the addition of solutes such as sugars will elevate this value substantially. The numerical value of Tg is a function of the weighted average molecular weight of the solutes in the solution.
Traditional ice cream manufacturing practice advocates the forming, shaping and packaging of the product close to the extrusion temperature (−4° C. to −7° C.) of ice cream when about 40 to 60% of the water in the product is frozen. In this state the product is still relatively soft and pliable and exhibits strong surface-adhesive properties. When this frozen mass is cooled further to lower temperatures a greater percentage of the water is frozen to ice and the product becomes hard and less pliable. A frozen beverage like a milkshake or smoothie is often prepared by mixing handscooped ice cream or sherbet with milk or water followed by blending using various mechanical means. While this technique is well established, it is generally conducted in fast food or restaurant establishments and not convenient for a user in the home due to the amount of equipment and effort needed to prepare a single serving.
A relatively recent trend has been towards the use of cryogenic freezing to make small beads or discrete particles or beads of predominantly spherical shape by immersion or exposure to a very cold environment such as liquid nitrogen. During these processes small droplets of liquid mix undergo a very rapid or instant drop in temperature which freezes them to a temperature below the glass transition temperature. Examples of this are found in U.S. Pat. Nos. 4,982,577, 5,438,839 and 6,223,542; US patent publications 2005/0008754A1 and 2006/0196194A1; and PCT publication WO2006/007922. As long as these cryogenically frozen particles are stored below the Tg, they will remain free flowing and not stick to each other.
Attempts have been made to use these particles for the preparation of frozen beverages in individual portions by adding a liquid such as milk to a container partially filled with these particles and shaking vigorously by hand after closing with a lid. This has not been satisfactory to date since the ice particles tend to clump together or adhere after contact with liquid. This detracts from the organoleptic properties that are desired in such products and requires further attention to break up these clumps. Generally, the level or degree of hand shaking that is necessary to break up these clumps is too high for the ordinary user, and while agitation with a spoon, whisk or manual or automatic mixing device can break up the clumps, this defeats the purpose of trying to make the product in a simple manner.
To facilitate easier mixing of the ice particles with a liquid it was thought to be desirable to provide the particles with a finer size and higher surface area to volume ratio. One way of achieving this is by converting the liquid mix to smaller entities like droplets or mist before rapidly freezing by exposing to a cryogenic medium such as liquid nitrogen. This is described in German patent DE 197 50 679, which relates to the production of ice particles from an aerated liquid mix or foam. Even though finer particles do mix more easily with a liquid, there remains a tendency for clumping or sticking after contact with the liquid and agitation still is required to make the final product.
Accordingly, there is a need for ice containing particles having enhanced properties for use in making frozen ice drink products without requiring extensive mixing, and these are now provided by the present invention.